Clopidogrel is an inhibitor of ADP-induced platelet aggregation acting by direct inhibition of adenosine diphosphate (ADP) binding to its receptor and of the subsequent ADP-mediated activation of the glycoprotein GPIIb/IIIa complex.
Clopidogrel bisulfate of formula I, is chemically known as, methyl (+)-(S)-α(2-chlorophenyl)-6,7-dihydrothieno[3,2-c]pyridine-5(4H)-acetate sulfate (1:1).

Clopidogrel hydrochloride of formula II is chemically known as, methyl (+)-(S)-α-(2-chlorophenyl)-6,7-dihydrothieno[3,2-c]pyridine-5(4H)-acetate hydrochloride. Clopidogrel and its salts are used in the treatment of platelet aggregation inhibitory and anti-thrombotic effect.

U.S. Pat. No. 4,529,596 discloses a racemic mixture of clopidogrel and processes for its preparation. U.S. Pat. No. 5,036,156 discloses a process for preparing an intermediate, 2-chloro-α-bromophenylacetic acid, which is useful in the synthesis of clopidogrel.
U.S. Pat. Nos. 4,847,265; 5,132,435; 6,215,005 and 6,258,961 disclose the processes for separating the S (+)-enantiomer of clopidogrel.
U.S. Pat. No. 6,800,759 discloses a process for resolution of racemic clopidogrel and racemization of R (−) enantiomer.
A problem with the preparation of clopidogrel is the presence of a therapeutically inactive enantiomer, the R (−) enantiomer. The presence of the R (−) enantiomer results in contamination of the final product, and lowers the yield. The skilled artisan is aware of few racemization processes utilizing a base. However, there exists a need for an industrial process for recycling the R (−) enantiomer via racemization and resolving the desired enantiomers. This recycling of the R (−) enantiomer improves the overall yield of the product and makes this process cost effective.